Heterocyclic compounds as antiallergic agents

ABSTRACT

There are disclosed compounds of the formula ##STR1## wherein X is --O--, --S-- or ##STR2## Y is --CH 2  O--, --OCH 2  --, --CH 2  S--, --SCH 2  --, ##STR3## m is 1-3; A is O or NR 2  ; 
     B is OR 2  ; SR 2  or N(R 2 ) 2  ; 
     R 1  is hydrogen, loweralkyl, loweralkoxy or halo; 
     R 2  is hydrogen or loweralkyl; 
     and the pharmaceutically acceptable salts thereof, and their use in the treatment of leukotriene-mediated naso-bronchial obstructive airpassageway conditions, such as allergic rhinitis, allergic bronchial asthma and the like.

This invention relates to novel heterocyclic compounds possessing lipoxygenase inhibitory and slow-reacting substance of anaphylaxis (SRS-A) antagonist activity which are useful as anti-inflammatory and antiallergic agents.

It is known that arachidonic acid (AA) is metabolized in mammals by two distinct pathways. The metabolism of arachidonic acid by cyclooxygenase enzymes results in the production of prostaglandins and thromboxanes. The physiological activity of these AA metabolites has been amply elucidated in recent years. The other pathway of AA metabolism involves lipoxygenase enzymes and results in the production of a number of oxidative products called leukotrienes. The latter are designated by the LT nomenclature system, and the most significant products of the lipoxygenase metabolic pathway are the leukotrienes C₄ and D₄. The substance denominated slow-reacting substance of anaphylaxis (SRS-A) has been shown to consist of a mixture of leukotrienes, with LTC₄ and LTD₄ as the primary products and having varying amounts of other leukotriene metabolites [see Bach et al., J. Immun. 215, 115-118 (1980); Biochem. Biophys. Res. Commun. 93, 1121-1126 (1980)].

The significance of these leukotrienes is that a great deal of evidence is accumulating showing the leukotrienes participate in inflammatory reactions, exhibit chemotactic activities, stimulate lysosomal enzyme release and act as important factors in the immediate hypersensitivity reaction. It has been shown that LTC₄ and LTD₄ are potent bronchoconstrictors of the human bronchi [see Dahlen et al., Nature 288, 484-486 (1980)], and another leukotriene, LTB₄, is a powerful chemotactic factor for leukocytes [see A. W. Ford-Hutchinson, J. Roy. Soc. Med., 74, 831-833 (1981)]. The activity of leukotrienes and slow-reacting substances (SRS's) as mediators of inflammation and hypersensitivity is extensively reviewed in Bailey and Casey, Ann. Reports Med. Chem., 17, 203-217 (1982).

The biological activity of the leukotrienes and SRS's, and of lipoxygenase as the enzyme leading to the metabolism of AA to leukotrienes, indicates that a rational approach to drug therapy to prevent, remove or ameliorate the symptoms of allergies, anaphylaxis, asthma and inflammation must focus on either blocking the release of mediators of these conditions or to antagonize their effects. Thus, compounds which inhibit the biological effects of the leukotrienes and SRS's and/or which control the biosynthesis of these substances, as by inhibiting lipoxygenase, are considered to be of value in treating such conditions as allergic bronchial asthma, allergic rhinitis, as well as in other immediate hypersensitivity reactions.

The invention provides novel compounds of the formula ##STR4## wherein X is --O--, --S-- or ##STR5## Y is --CH₂ O--, --OCH₂ --, --CH₂ S--, --SCH₂ --, ##STR6## m is 1-3; A is O or NR² ;

B is OR², SR² or N(R²)₂ ;

R¹ is hydrogen, loweralkyl, loweralkoxy or halo;

R² is hydrogen or loweralkyl;

and pharmaceutically acceptable salts thereof.

The term "halo" refers to fluoro, chloro, and bromo. The terms "loweralkyl" and "loweralkoxy" refer to moieties having 1-6 carbon atoms in the carbon chain.

The compounds of the invention can be prepared in a number of ways. The basic compounds, with the moiety ##STR7## such as a 2-pyrrolidinone, can be prepared by the following reaction sequence in which Y is --CH₂ O--: ##STR8## Compounds in which the bridge Y is --CH₂ S-- and --CH₂ N-- can be prepared in a like manner, using the appropriate aminothiophenol or aminoaniline in place of the aminophenol. Compounds in which the bridge Y is ##STR9## can be prepared by using the appropriate heterocyclic acyl chloride or acyl N-imidazole and the appropriate N-substituted aminoaniline.

The starting compounds for the preparation of compounds in which the linking bridge Y is --O--, --S-- or ##STR10## can be prepared by the following reaction sequence: ##STR11## where the appropriate starting compounds are commercially available or can be conveniently prepared by conventional preparative techniques.

Compounds of the invention in which B in the moiety ##STR12## is other than --OR² are prepared using the carboxyl group, ##STR13## wherein R² is hydrogen, as the starting intermediate. Thus, for example, compounds in which B in the group ##STR14## is --SR² are prepared in the following manner: ##STR15## In like manner, after activation of the carboxyl group, it is possible to prepare the amides, as for example in the following sequence: ##STR16##

Compounds of the invention in which the group A in the moiety ##STR17## is NR² and B is --OR², --SR² or --N(R²)₂ are likewise prepared by using the carboxyl group as the starting intermediate. The initial reaction sequence is as follows: ##STR18## The resulting nitrile is then used in a Pinner reaction, using suitable reactants, to prepare the desired compounds. Thus, the appropriate reactions are as follows: ##STR19##

In all instances, the starting compounds used in the reaction sequences are either commercially available or can be readily prepared by conventional preparative methods readily apparent to those skilled in the art.

Compounds of the invention which contain a basic nitrogen are capable of forming pharmacologically acceptable salts, including the salts of pharmacologically acceptable organic and inorganic acids such as hydrochloric, hydrobromic, sulfuric, nitric, phosphoric, methanesulfonic, benzenesulfonic, acetic, citric, fumaric, maleic, succinic and the like. The compounds which are carboxylic acids or have a hydroxamic function are capable of forming alkali metal and alkaline earth carboxylates and carboxylates of pharmacologically acceptable cations derived from ammonia or a basic amine. Examples of the latter include but are not limited to cations such as ammonium, mono-, di-, and trimethylammonium, mono-, di- and triethylammonium, mono-, di-, and tripropylammonium (iso and normal), ethyldimethylammonium, benzyldimethylammonium, cyclohexylammonium, benzylammonium, dibenzylammonium, piperidinium, morpholinium, pyrrolidinium, piperazinium, 1-methylpiperidinium, 4-ethylmorpholinium, 1-isopropylpyrrolidinium, 1,4-dimethylpiperazinium, 1-n-butyl-piperidinium, 2-methylpiperidinium, 1-ethyl-2-methylpiperidinium, mono-, di- and triethanolammonium, ethyl diethanolammonium, n-butylmonoethanolammonium, tris(hydroxymethyl)methylammonium, phenylmonoethanolammonium, and the like.

The compounds of the invention, by virtue of their ability to inhibit the activity of lipoxygenase enzyme and by their ability to antagonize the effects of LTD₄ and LTC₄, which are the major constituents of SRS-A, are useful for the inhibition of symptoms induced by these leukotrienes. Accordingly, the compounds are indicated in the prevention and treatment of those disease states in which LTD₄ and LTC₄ are causative factors, for example allergic rhinitis, allergic bronchial asthma and other leukotriene mediated naso-bronchial obstructive air-passageway conditions, as well as in other immediate hypersensitivity reactions, such as allergic conjunctivitis. The compounds are especially valuable in the prevention and treatment of allergic bronchial asthma.

When the compounds of the invention are employed in the treatment of allergic airways disorders, they can be formulated into oral dosage forms such as tablets, capsules and the like. The compounds can be administered alone or by combining them with conventional carriers, such as magnesium carbonate, magnesium stearate, talc, sugar, lactose, pectin, dextrin, starch, gelatin, tragacanth, methylcellulose, sodium carboxymethylcellulose, low melting wax, cocoa butter and the like. Diluents, flavoring agents, solubilizers, lubricants, suspending agents, binders, tablet-disintegrating agents and the like may be employed. The compounds may be encapsulated with or without other carriers. In all cases, the proportion of active ingredients in said compositions both solid and liquid will be at least to impart the desired activity thereto an oral administration. The compounds may also be injected parenterally, in which case they are used in the form of a sterile solution containing other solutes, for example, enough saline or glucose to make the solution isotonic. For administration by inhalation or insufflation, the compounds may be formulated into an aqueous or partially aqueous solution, which can then be utilized in the form of an aerosol.

The dosage requirements may vary with the particular compositions employed, the route of administration, the severity of the symptoms presented and the particular subject being treated. Treatment will generally be initiated with small dosages less than the optimum dose of the compound. Thereafter the dosage is increased until the optimum effect under the circumstances is reached. In general, the compounds of the invention are most desirably administered at a concentration that will generally afford effective results without causing any harmful or deleterious side effects, and can be administered either as a single unit dose, or if desired, the dosage may be divided into convenient subunits administered at suitable times throughout the day.

The lipoxygenase inhibitory and leukotriene antagonist effects of the compounds of the invention may be demonstrated by standard pharmacological procedures, which are described more fully in the examples given hereinafter.

These procedures illustrate the ability of the compounds of the invention to inhibit the polymorphonuclear leukocyte synthesis of the lipoxygenase products 5-HETE and 5,12-di-HETE and the ability of the compounds to antagonize LTC₄ and LTD₄ -induced bronchospasm mediated by exogenously administered leukotrienes.

The following examples show the preparation and pharmacological testing of compounds within the invention.

EXAMPLE 1 N-[3-[(2-Benzthiazolyl)methoxy]phenyl]pyrrolidin-2-on-4-carboxylic acid, methyl ester

A. 2-chloromethylbenzthiazole

To a solution of aminothiophenol (8.3 g) in methylene chloride at 0° C. is added methyl chloroacetimidate hydrochloride [prepared according to procedures described by R. Rogers and D. G. Nielson, Chem. Rev., 61, 179 (1961)] (8.6 g). The reaction is allowed to warm to room temperature while stirring overnight. The mixture is washed with water (3X); dried over magnesium sulfate and concentrated to an oil. The oil is distilled (120°-135° C. at 0.5 mm Hg) to give 7.8 g (71% yield) of product.

B. N-(3-phenol)-pyrrolidin-2-on-4-carboxylic acid

A mixture of 3-aminophenol (10.9 g) and itaconic acid (13.0 g) is heated to 120°-130° C. for 5 minutes. After cooling, a solid forms giving 21.5 g (97% yield) of product, m.p. 214°-215° C.

C. N-(3-phenol)-pyrrolidin-2-on-4-carboxylic acid, methyl ester

A solution of N-(3-phenol)-pyrrolidin-2-on-4-carboxylic acid (21.0 g) in methanol with para-toluenesulfonic acid (0.1 g) is heated to reflux. The reaction is refluxed for four days while water is removed using a Soxhlet extractor filled with 3A molecular sieves. The mixture is cooled and a solid forms which is filtered and dried giving 9.5 g (42% yield) of product, m.p. 178°-180° C.

D. N-[3-[(2-benzthiazolyl)methoxy]phenyl]pyrrolidin-2-on-4-carboxylic acid, methyl ester

A mixture of 2-chloromethylbenzthiazole (3.12 g), N-(3-phenol)-pyrrolidin-2-on-4-carboxylic acid, methyl ester (4.0 g), cesium carbonate (5.3 g), sodium carbonate (1.8 g), potassium iodide (0.1 g) and acetone (200 ml) is heated at reflux overnight. The mixture is filtered and the resulting solution concentrated to an oil. The oil is triturated with ether forming a solid which is filtered and dried giving 4.0 g (62% yield), m.p. 99°-102° C.

Analysis for: C₂₀ H₁₈ N₂ O₄ S Calculated: C, 62.81; H, 4.74; N, 7.32 Found: C, 62.39; H, 4.75; N, 7.26.

EXAMPLE 2

Following the procedure of Example 1 and using appropriate starting materials and reagents, the following compounds are prepared:

A. N-[3-[(1-methyl-2-benzimidazolyl)methoxy]phenyl]pyrrolidin-2-on-4-carboxylic acid, methyl ester, m.p. 131°-132.5° C.

Analysis for: C₂₁ H₂₁ N₃ O₄ Calculated: C, 66.47; H, 5.57; N, 11.07 Found: C, 66.12; H, 5.51; N, 11.02.

N-[3-[(2-benzoxazolyl)methoxy]phenyl]pyrrolidin-2-on-4-carboxylic acid, methyl ester, m.p. 107°-108.5° C.

Analysis for: C₂₀ H₁₈ N₂ O₅ Calculated: C, 65.56; H, 4.95; N, 7.64 Found: C, 65.29; H, 4.98; N, 7.51.

EXAMPLE 3

The compounds 5- and 12-hydroxyeicosatetraenoic acid (5-HETE and 12-HETE) and 5,12-dihydroxyeicosatetraenoic acid (5,12-diHETE) are early arachidonic acid oxidation products in the lipoxygenase cascade, which have been shown to mediate several aspects of inflammatory and allergic response. This is especially true with respect to 5,12-diHETE, which is also denoted as LTB₄ [see Ford-Hitchinson, J. Roy. Soc. Med., 74, 831 (1981)]. The assay of this Example measures the ability of the compounds of the invention to inhibit the synthesis of 5-HETE and LTB₄ by rat glycogen-elicited polymorphonuclear leukocytes.

The assay is carried out as follows:

Peritoneal PMN are obtained from female Wistar rats (150-250 g) that received an i.p. injection of 6% glycogen (10 ml). After 24 hours, rats are killed by CO₂ asphyxiation and peritoneal cells are harvested by peritoneal lavage using Ca⁺⁺ and Mg⁺⁺ free Hanks' balanced salt solution (HBSS). The peritoneal exudate is centrifuged at 400 g for 10 minutes. After centrifugation, the lavaged fluid is removed and the cell pellet is resuspended in HBSS containing Ca⁺⁺ and Mg⁺⁺ and 10 mM L-cysteine at a concentration of 2×10⁷ cells/ml. To 1 ml portions of cell suspension, test drugs or vehicle are added and incubated at 37° C. for 10 minutes. Following this preincubation, the calcium ionophore (10 μM), A23187, is added together with 0.5 μCi[¹⁴ C]arachidonic acid and further incubated for 10 minutes. The reaction is stopped by the addition of ice cold water (3 ml) and acidifying to pH 3.5. Lipoxygenase products are then extracted twice into diethyl ether. The pooled ether extracts are evaporated to dryness under nitrogen and the residue is redissolved in a small volume of methanol and spotted on aluminum backed pre-coated thin layer chromatographic plates. The samples are then co-chromatographed with authentic reference 5-HETE, 12-HETE and 5,12-diHETE in the solvent system--hexane:ether:acetic acid (50:50:3). After chromatography, the areas associated with 5-HETE and 5,12-diHETE standards are identified by autoradiography, cut out and quantitated by liquid scintillation.

Results are expressed as % inhibition of [¹⁴ C]5-HETE and [¹⁴ C]LTB₄ (5,12-HETE) synthesis. ##EQU1##

Testing compounds of the invention in this assay and using the antioxidant 3-amino-1-[m-(trifluoromethyl)phenyl]-2-pyrazoline (BW755C) as a standard, the following results are obtained.

                  TABLE I                                                          ______________________________________                                                          50% Inhibitory                                                Compound of      Concentration (IC.sub.50) μm                               Example Number   5-HETE   LTB.sub.4                                            ______________________________________                                         BW755C           43.00    30.00                                                               % Inhibition at 100 μm                                       1                94.30    84.50                                                2A               34.60    32.30                                                2B               87.20    82.80                                                ______________________________________                                    

The results show that compounds of this invention have significant activity in inhibiting the synthesis of the arachidonic acid lipoxygenase oxidation products 5-HETE and LTB₄.

EXAMPLE 4

The assay of this Example measures the in vivo ability of the compounds of the invention to inhibit the bronchospasm induced in guinea pigs by the exogenously administered leukotrienes C₄ and/or D₄. This assay is essentially a measure of the SRS-A antagonist properties of the compounds tested.

This assay is carried out as follows:

Male Hartley strain guinea pigs (350-600 g) are anesthetized with pentobarbital sodium (50 mg/kg, i.p.). The jugular vein is cannulated for injection of drugs and the carotid artery for monitoring blood pressure. The trachea is cannulated for artificial ventilation by a miniature Starling pump and for indirect measurement of respiratory volume changes as described infra. Additional pentobarbital sodium (15 mg/kg, i.v.) is administered to arrest spontaneous respiration. Submaximal bronchoconstrictor responses are established in control animals by varying the dose-levels of leukotriene. Intravenous dose-levels for LTC₄ range from 1 to 2 μg/kg and for LTD₄ the range is from 0.3 to 1 μg/kg. The aerosol bronchoprovocation dose for LTC₄ is generated from 1.6 μM solution and for LTD₄ from a 2.0 μM solution.

Test drugs are administered either intravenously, intraduodenally, by aerosol or orally at 1 or 10 minutes before induction of bronchospasm by administration of either LTC₄ or LTD₄ at the predetermined dose-levels. Aerosols of soluble drugs or leukotrienes are produced in-line for 10 seconds only by actuation of an ultrasonic nebulizer (Monaghan). Aerosolized drug dosage is expressed in terms of solution concentration and by a fixed aerosol exposure time (approximately 10 seconds). Control animals receive saline in place of drug.

Respiratory volume changes are determined by a calibrated piston whose travel is recorded, via a linear transducer, on a Beckman Dynograph recorder. Maximal bronchoconstrictor volume is determined by clamping off the trachea at the end of the experiment. Overflow volumes at 1, 3 and 5 minutes are obtained from the recorded charts.

The overflow volume at 1, 3 and 5 minutes is expressed as a percentage of maximal bronchoconstriction. Combined group values are used from each of these time intervals to determine the inhibitory effect of drugs. ##EQU2## Students t-test for unpaired data is used to determine statistical significance. Dose response curves are generated and ED₅₀ doses are interpolated from the regression lines.

Results for a compound of the invention in this assay, using LTD₄ for induction of bronchospasm, is given below:

                  TABLE II                                                         ______________________________________                                         Compound administered at 10 minutes before                                     induction of bronchospasm                                                                 Dose        % Inhibition                                            Compound of                                                                               mg/kg       Overflow Volume at                                      Example Number                                                                            (Intraduodenal)                                                                            1 min.   3 min.                                                                               5 min.                                   ______________________________________                                         1          50          72       66    68                                       2A         50          56       20    18                                       2B         50          26       12    15                                       ______________________________________                                    

The results show that compounds of the invention show in vivo activity against LTD₄ induced bronchoconstriction. 

What is claimed is:
 1. A compound having the formula ##STR20## wherein X is --O--, --S-- or ##STR21## Y is --CH₂ O--, --OCH₂ --, --CH₂ S--, --SCH₂ --, ##STR22## m is 1-3; A is O or NR² ;B is OR², SR² or N(R²)₂ ; R¹ is hydrogen, loweralkyl, loweralkoxy or halo; R² is hydrogen or loweralkyl;and the pharmaceutically acceptable salts thereof.
 2. The compound of claim 1, which is N-[3-[(2-benzthiazolyl)methoxy]phenyl]pyrrolidin-2-on-4-carboxylic acid, methyl ester.
 3. The compound of claim 1, which is N-[3-[(1-methyl-2-benzimidazolyl)methoxy]phenyl]pyrrolidin-2-on-4-carboxylic acid, methyl ester.
 4. The compound of claim 1, which is N-[3-[(2-benzoxazolyl)methoxy]phenyl]pyrrolidin-2-on-4-carboxylic acid, methyl ester. 